Project 1

Hydrological variability of the Intertropical Convergence Zone in equatorial East Africa over the past 25,000 years

Lake Challa from equatorial East Africa forms a key site to analyse the hydrological variability of the Intertropical Convergence Zone over the past 25,000 years.

External climate influences - such as changes in solar radiation or insolation - generate different responses in different regions. There are extensive records from high and low latitudes with which to assess the relationship between insolation and climate variability. But tropical records are much rarer, and records from regions in the path of the Intertropical Convergence Zone, which produces the monsoonal climate of alternating wet and dry seasons, are rarer still. Dr Maarten Blaauw, collaborated in the study with PI Prof. Verschuren, Ghent University Belgium which reports on one such record and analyses proxies of hydrologic variability in the 25,000-year sediment sequence of Lake Challa, a crater lake on the slopes of Mount Kilimanjaro. The archive, which was dated at very high precision in the Belfast carbon dating laboratory (in collaboration with other laboratories), shows that monsoon rainfall in East Africa varied in cycles of about 11,500 years, in phase with orbitally controlled solar radiation forcing.